Moving funds from your account funds (which will automatically be used by all of your farms as needed) to an individual farm is easy; go to the individual farm page, Billing tab, “My Deposit”, and transfer funds in.
However, is there any way to move funds from a farm back to the main user account? For example, if you moved your funds to an individual farm but want it back in your main account funds to automatically pay multiple farms (rather than needing to manually fund each one). Seems like this should be possible.